The foot

This element is one of the easiest but also may be the most important of the whole system.The embroidery foot has two functions hold the fabric when the needle come out and detect when the needle comes out of the fabric.

After several attempts of 3D feet we decided to use one sold in markets for ‘free embroidery’ to which we added a sensor.
This solution revealed to be the best since it has been working with us for over a year now with very good results.

Even though we made all of our firs tests without a presser foot (up until summer 2015) it was revealed very necessary to make the machine work perfectly. In order to understand why let me explain how a sewing machine works.

An animated GIF is better then a long talk.

The needle slides in the fabric and when it just starts to pull up the claws of the bobbin (pink)it hangs on the thread and make it turn around the bobbin.

The tension mechanism (not shown here) pulls up the top thread (purple) and reduces the loop formed by the thread bringing the thread from the green bobbin in the center of the fabric.

In most recent machines the claw/bobbin part is placed horizontally and on some very old machines he uses a oscillating claw instead of a rotary one. It doesn’t change anything to the way the machine works.

What we are looking at here is the little loop the needle makes when it pulls back up before the claw. It ease the capture of the thread, without it the claw can miss the capture which often lead to jamming or to jumps a stitch.
This loop is formed by the friction between the thread and the fabric during the rise.
With no foot the fabric pulls-up with the thread , in that case there is no loop….

The detect the needle we use a optical sensor to prevent the mechanics to wear off.
A simple optical angle sensor is fixed at the back of the foot and the beam is cut by a tiny 3D piece on a metallic element of the foot.